Air-to-air heat pumps installed in 2018 or more recently, in pre-existing (not new construction) principal (primary, not rental) homes may be eligible for a $300 tax credit through 2020. You can go back and claim the credit by amending a previous tax return. Details.
Ground-source heat pumps have a similar program.
We recommend consulting a tax-preparer to take advantage of this opportunity, but here are the Instructions and the Form for taking advantage of this opportunity. If you’re a Turbo Tax user, the info found HERE may be helpful in directing you to the proper place to claim the credit.